Dehydration of pentaerythritol esters and preparation of resins from said dehydrated esters



DEHYDRATION F PENTAERYTHRITOL ESTERS AND PREPARATION OF RESINS FROM SAID DEHYDRATED ESTERS William M. Kraft, Verona, N.J., assignor to Heyden Newport Chemical Corporation, a corporation of Delaware No Drawing. Filed Aug. 22, 1955, Ser. No. 529,921

Claims. (Cl. 260-22) The present invention relates to the production of pentaerythritol reaction products including pentaerythritol alkyd resins having unexpected and highly desirable characteristics. While the present invention will be described more particularly in connection with the production of alkyd resins, its principles are applicable to the production of pentaerythritol reaction products which in addition to being useful in the production of alkyd resins are useful in preparing drying oils, paints and other products.

Alkyd resins are produced by reacting a polyhydric alcohol and a polycarboxylic acid. The polycarboxylic acid may be an aliphatic acid, for example, maleic acid, fumaric acid, succinic acid, sebasic acid and adipic acid, or an aromatic acid, for example, phthalic acid, terephthalic acid and isophthalic acid, or a non-aromatic acid, for example, tetrahydrophthalic acid and hexahydrophthalic acid. Mixtures of such acids can be used and the anhydrides of the acids can be used with the same results. For the sake of brevity, the term acid when in connection with polycarboxylic acids shall include the anhydride. Phthalic acid and phthalic anhydride, for example, can be used interchangeably. The polyhydric alcohol may be for example, glycerin, glycol, propylene glycol, diethylene glycol, pentaerythritol, dipentaerythritol, mannitol or mixtures thereof. The particular acid or combination of acids as well as the particular polyhydric alcohol or combination of alcohols depends on the characteristics desired in the alkyd resin.

Highly satisfactory alkyd resins which are especially useful in preparing architectural finishes are the pentaerythritol and dipentaerythritol types of alkyds. The alkyd resins prepared with dipentaerythritol are, in general, superior to those prepared from pentaerythritol.

For example, dipentaerythritol-phthalic acid resins form films which are harder and more resistant to water and alkali than similar films formed from pentaerythritolphthalic acid resins. However, dipentaerythritol is produced commercially only as a by-product in the production of pentaerythritol. When acetaldehyde and formaldehyde are condensed in an aqueous medium containing an alkaline condensation catalyst to produce pentaerythritol commercially, a relatively small amount of the polyhydric product, for example, about 12%, is dipentaerythritol. This limits the production of dipentaerythritol and it is not always available for use either alone or with pentaerythritol to form alkyd resins.

It has been discovered that pentaerythritol partially: esterified with a monocarboxylic acid can be dehydrated in the presence of a dehydration catalyst to form a reac-" tion product which upon reaction with a dicarboxylic acid,

forms an alkyd resin having properties similar to those of 7 alkyd resins obtained by reacting dipentaerythritol and. the

same acids. In other words, the partially esterified pentaerythritol can be dehydrated to form a productwhich is similar in properties to dipentaerythritol having the same degree of esterification. The esterification reaction may 2,985,601 Patented May 23, 1961 too Any of the monocarboxylic acids commonly used in the production of alkyd resins may be used for present purposes. The monocarboxylic acid may be an aliphatic or aromatic acid, for example, a higher fatty acid containing 6-18 carbon atoms, benzoic acid, or mixtures thereof. The acids of drying and semi-drying oils may be used as well as lauric and caproic acids. The degree of esterification may range from 1 to 3 moles of monocarboxylic acid per mole of pentaerythritol. About one mole of acid is required to obtain the desired results while esterification by more than 3 moles of acid unduly reduces the hydroxyl content and the formation of ether linkages upon dehydration. Preferably, the pentaerythritol is esterified with about 1 to 2 moles of acid per mole of pentaerythritol and very good results have been obtained with a ratio of about 1.3 moles of acid per mole of pentaerythritol. The degree of esterification is expressed as moles of acid per mole of pentaerythritol, it being understood that this is the average esterification. The following reaction illustrates the esterification reaction which accompanies or precedes the dehydration reaction:

carton no CHT-C-CHflOHFZCHiKCHQQC 0 on mon omoocwmncn, no cap OHOH +2mo CHzO O C (CH2)lCHa' The properties of the pentaerythritol reaction product as well as the properties of the alkyd resins, or other products produced therefrom, depend on the amount of water removed as a result of dehydration. The removal of at least 0.4 mole of water per mole of pentaerythritol is desirable to obtain a noticeable improvement of the type customarily associated with the use of dipentaerythritol. If more than 0.8 mole of water per mole of pentaerythritol is removed by dehydration, the reaction proceeds very slowly and there is a tendency to produce insoluble by-products, which may be higher pentaerythritol ether-esters. Preferably, 0.45-0.65 mole of water is removed by dehydration. Indications are that the present pentaerythritol ester contains at least 10% to 30% of the dipentaerythritol ester. Dehydration of one mole of pentaerythritol ester to form a half mole of dipentaerythritol ester would require theoretically the removal of 0.5 mole of water in accordance with the following reaction:

CHzO O C 0 7113:

Representatives of the dehydration catalysts are the phosphorus and sulfur containing acids, phosphoric acid,

precede dehydration or take place substantially simultane-' 'ously therewith. Apparently, the ester groups direct or pyrophosphoric acid and p-toluene sulfonic acid. These catalysts have been used in amounts ranging from l.0-2.5% by Weight based on the pentaerythritol content. Largeror' smaller amounts of these and other dehydration catalysts may be used. Heating is desirable to eifect more rapidly the esterification and dehydration reaction.

The following examples illustrate the present invention. All parts and percentages are by weight.

EXAMPLE I One mole (146 grams) of technical pentaerythritol for 11 hours to form a partially esterified pentaerythritol ether:

containing about 12% dipentaerythritol was mixed with Mono pentaerythritol 136 grams (1 mole). 1.3 moles (370 grams) of soybean oil fatty acids and 2 5 Benzoic acid 122 grams (1 mole). grams of phosphoric acid. The mixture was heated at p-Toluene sulfonic ac1d 1.14 grams. 220 C. until a total of 1.75 moles of water had been Xylol 50 m1- removed. The removed water was formed as a result The xylobwater azeotrope was collected and 26 mL of of esterification and dehydration. The esterification reacwater was obtained in this matter Theoretically, the Produced moles of Water and the .iehydrajuon esterification reaction produces 18 ml. of water so that reaction produced 0.45 mole of water. ThlS esterified 8 mL of Water was formed as a result of dehydration and dehydrated pentaerythntol reaction product was Dehydration o pentaefythritolwfmm the pentaerythritol mlxed Wlth mole (80 grams) of soybfian 011 fatty ether, dipentaerythritol, should in theory produce 9 ml. acids and 1.0 mole (148 grams) of phthalic anhydride. Water. This mixture was heated at 230 C. until its acid number The partially esterified pentaerythfitol ether was fiup was less than 10. The properties of this alkyd resin are ther esterified with 244grams (2 moles) of .benzoic acid listed in the table included in Example II. by heating for 23 hours at 1962150 C. The syrupy EXAM E 11 product wasf coollgd andtbltlelnzene twa;l ad cllgld to zeflmit separation o a-w te crys a ne ma er1 i e crys a me In .thls Example a senes of alkyds were In material was separated by filtration and this 565 grams 621.611 Instance moles (370 grams) f Soybean 011 fatty of material had a melting point of 154-.l68 C. On re acids and 1 moi: grams? of techmcal Pemaerythm? crystallization from benzene, 50.5 grams of a product was heated at 2 i 2 grams of phospgloric obtained having a melting point of 183-184 C. which i Three estenfied. reactlon Products e is the melting point of dipentaeryt-hritol hexabenzoate. this manner y removmg and mo es 0 25 Dipentaerythritol hexabenzoate from another source was i" re.specuvely The Water formed as a result of mixed with the dipentaerythritol hexabenzoate produced estenficanon. males Then each dehydrated. ester in this manner without depressing the melting point. was .reacted wlth mole (.120 grams) of Phthahc The partially esterified pentaerythritol ether may be hydnde 9 form an alkyd 'i The prqpertles of these reacted with dibasic acid, for example, phthalic, acid, to three resins are set forth in the following table. lfor form an alkyd resin This Same intelmedl-ate; product purpqses of comganson the piopemes pelfltaerythntol may be mixed with, for example, drying oil, to form a and dlp-entaerythritol alkyd resins Prepared with the same modified drying Oil or may be used as Such in architec phthalate content are also given 1n this table. In each mral coatings instance, a thin film of the alkyd resin was formed by EXAMPLE 1v casting onto. a test tube a xylol solution containing 70% by weight of the alkyd resin. The film was air dried for l dlfiel'ent fiq P 'f were P P y 72 hours. Thereafter the coated test tube was immersed 'E Y 8 Pentaefythnml Wltl} famous u ts of c pin 3% aqueous sodium hydroxide to determine the alkali Tole Y Q was adfied P-Y f Y 0 resistance of the coating. A similar solution was cast Wate? were Temved dunng' esteflficatlofl; pa l in fil on fl t glass wide/[ermine drying time and fil esterified pentaerythntol was then dehydrated by heating hardness. The viscosity and color tests also were made 40 Wlth a dehydratlollfatalyst The amounts 0f reactants with a xylol solution containing of alkyd resin. the reaction conditions and characteristics of the reac- Table Drying Time, Sward Hardness Alkali Resistance, Minutes Molaot Hi0 of Gardner- Gardner Minutes (Glass-) Dehydration Holdt; (1933) Example No. 7 per Mole Pen- Viscosity Color of taerythritol of Xylol Xylol Setto Tack 1 7 14 First Consider- Complete Solution Solution Touch Free Day Days Days wlilnitgengltiilgck Failure 2- r 2 i8 1. 2 at as oi s 2-2 s 15 90 4 10 2s 15 260 2: 000 0.75 Z3 s 10 40 4 10 15 138 5,100

Alkyd none E 6% 90 150 4 6 5 15 20 Dipentaerythritol V Alkyd none Y 7 5 6 8 15 270 EXAMPLE III The following materials were heated at ISO- C.

tion products are set forth for the three runs in the i accompanying table.

No. 1 N6. 3

Caproic Acid (commercial) Pentaerythritol (pure) Temp. during esterification Heating period (hours) 119 g. (1 mole) 136 g. (1 mole)- :70-209 0 357 g. (3 moles). 136 g, (1 mole). l802250.

Mixture heated at Heating period (hours) Dehydrated product:

Percent OH-Foiiml Acid No.-Fo d Water removed by dehydration .553. we a; O

11.7.. 1.4. 9,ml. (0.5 mole)- 5.63- 1.3-. 9 ml. (0.5 mole)- 1. 0.39 molel'.

These esterified pentaerythritol ethers may be used in preparing alkyd resins. However, this type of product which is not esterified with siccative oil acids, is preferably used forvother purposes and, for example, it may be reacted with a drying oil to form a modified drying oil which may be used in paints.

In the foregoing Examples I and II, the esterified pentaerythritol ether used in producing the alkyd resins, was only partially esterified and contained reactive hydroxyl groups. While partial esterification is preferable so that the esterification plus dehydration does not account for all the hydroxyl groups, this reaction product need not contain hydroxyl groups. A pentaerythritol ether may be completely esterified. In other words the esterification and dehydration reactions may account for substantially all of the hydroxyl groups. Such a product, for example the dipentaerythritol hexabenzoate of Example II I may be subjected to alooholysis with a polyhydric alcohol and this reaction product can then be reacted with a polycarboxylic acid to form an alkyd resin. Alternatively, such a completely esterified pentaerythritol ether can he used in coatings, such as varnishes, lacquers and paints.

The dicarboxylic acid or anhydride reacted with the esterified pentaerythritol ether may be any of the dicarboxylic acids or their anhydrides used in the production of alkyds. The reaction of the dicarboxylic acid with the dehydrated pentaerythritol ester may follow alcoholysis of the dehydrated pentaerythritol ester. If the dehydrated pentaerythritol ester is only partially esterified this reaction product may be further esterified with monocarboxylic acid before reaction with the dicarboxylic acid or may be reacted directly with dicarboxylic acid to form an alkyd resin.

I claim: v

1. The method of producing pentaerythritol reaction products which comprises the steps of heating and esterifying pentaerythritol with 1 to 2 moles per mole of pentaerythritol of a monocarboxylic acid selected from the group consisting of fatty acids containing 6 to 18 carbon atoms, benzoicacid, and mixtures thereof at a temperature between approximately 150 C. and 230 C. to remove 1 mole of water of esterification per mole of acid and heating and dehydrating the partially esterified pentaerythritol at a temperature between approximately 150 C. and 230 C. in the presence of an acid dehydration catalyst to remove from 0.4 to 0.8 mole of water of dehydration per mole of pentaerythritol thereby forming a partially esterified dipentaerythritol-containing pentaerythritol reaction product.

2. The method of producing pentaerythritol reaction products which comprises the steps of heating and esterifying pentaerythritol with 1 to 2 moles per mole of pentaerythritol of a monocarboxylic acid selected from the group consisting of fatty acids containing 6 to 18 carbon atoms, benzoic acid, and mixtures thereof at a temperature between approximately 150 C. and 230 C. to remove 1 mole of Water of esterification per mole of acid and heating and dehydrating the partially esterified pentaerythritol at a temperature between approximately 150 C. and 230 C. in the presence of an acid dehydration catalyst to remove from 0.45 to 0.65 mole of water of dehydration per mole of pentaerythritol thereby forming a partially esterified dipentaerythritol-containing pentaerythritol reaction product.

3. The method of producing pentaerythritol reaction products which comprises the steps of forming a mixture comprising pentaerythritol, an acid dehydration catalyst, and from 1 to 2 moles of a monocarboxylic acid per mole of pentaerythritol, said monocarboxylic acid being selected from the group consisting of fatty acids containing 6 to 18 carbon atoms, benzoic acid, and mixtures thereof, and heating said mixture at a temperature between approximately 150 C. and 230 C. to substantially simultaneously esterify the pentaerythritol with said monocarboxylic acid and dehydrate the pentaeryth- 73 220 products which comprises the steps of forming a mixture comprising pentaerythritol, an acid dehydration catalyst, and from 1 to 2 moles of a monocarboxylic acid per mole of pentaerythritol, said monocarboxylic acid being selected from the group consisting of fatty acids containing 6 to 18 carbon atoms, benzoic acid, and mixtures thereof, and heating said mixture at a temperature between approximately C. and 230 C. to substantially simultaneously esterify the pentaerythritol with said monocarboxylic acid and dehydrate the pentaerythritol partial ester formed thereby obtaining a partially esterified dipentaerythritol-containing pentaerythritol reaction product and water, the total amount of water present including 1 mole of water of esterification per mole of acid and from 0.45 to 0.65 mole of water of dehydration per mole of pentaerythritol.

5. The method of producing pentaerythritol reaction products which comprises the steps of forming a mixture comprising pentaerythritol, an acid dehydration catalyst, and about 1.3 moles of a carboxylic acid per mole of pentaerythritol, said monocarboxylic acid being selected from the group consisting of fatty acids containing 6 to 18 carbon atoms, benzoic acid, and mixtures thereof, and heating said mixture at a temperature between approximately 150 C. and 230 C. to substantially simultaneously esterify the pentaerythritol with said monocarboxylic acid and dehydrate the pentaerythritol partial ester formed thereby obtaining a partially esterified pentaerythritol reaction product containing at least 10% of partially esterified dipentaerythritol and Water, the total amount of water present including 1 mole of water of esterification per mole of acid and from 0.4 to 0.8 mole of water of dehydration per mole of pentaerythritol.

6. The method of producing pentaerythritol reaction products which comprises the steps of heating and partially esterifying pentaerythritol with from 1 to 2 moles per mole of pentaerythritol of a monocarboxylic acid selected from the group consisting of fatty acids containing 6 to 18 carbon atoms, benzoic acid, and mixtures thereof at a temperature between approximately 150 C. and 230 C. thereby forming and removing 1 mole of Water of esterification per mole of acid and thereafter heating and dehydrating at a temperature between approximately 150 C. and 230 C. in the presence of an acid dehydration catalyst the partially esterified pentaerythritol to remove from 0.45 to 0.65 mole of water of dehydration per mole of pentaerythritol thereby forming a partially esterified pentaerythritol reaction product containing at least 10% of partially esterified dipentaerythritol.

7. In the process of producing alkyd resins, the steps comprising heating and partially esterifying pentaerythritol with 1 to 2 moles per mole of pentaerythritol of a monocarboxylic acid selected from the group consisting of fatty acids containing 6 to 18 carbon atoms, benzoic acid, and mixtures thereof at a temperature between approximately 150 C. and 230 C. to form 1 mole of water of esterification per mole of acid, heating and dehydrating the partially esterified pentaerythritol at a temperature between approximately 150 C. and 230 C. in the presence of an acid dehydration catalyst to form from 0.4 to 0.8 mole of Water of dehydration per mole of pentaerythritol thereby forming a partially esterified dipentaerythritol-containing reaction product, and thereafter heating said partially esterified reaction product at a temperature between approximately C. and 230 C. with an acid selected from the 7 group consisting of maleic acid, fumaric acid, succinic acid, sebacic acid, adipic acid, phthalic acid, terephthalic acid, .isophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and the anhydrides of said acids, said acid being present in an amount that is substantially equivalent stoichiometrically to the amount of said partially esterified pentaerythritol reaction product that is present, thereby forming an alkyd resin.

8. In the process of producing alkyd resins, the steps comprising heating and partially esterifying pentaerythritol with 1.3 moles per mole of pentaerythritol of a monocarboxylic acid selected from the group consisting of fatty acids containing 6 to '18 carbon atoms, benzoic acid, and mixtures thereof at a temperature between approximately 150 C. and 230 C. to form 1 mole of water of esterification per mole of acid, heating and dehydrating the partially esterified pentaerythritol at a temperature between approximately 150 'C. and 230 C. in the presence of an acid dehydration catalyst to form from 0.45 to 0.65 mole of water of dehydration per mole of pentaerythritol thereby forming a partially esterified dipentaerythritol-containing pentaerythritol r6- action product, and thereafter heating said partially esterified reaction product at a temperature between approximately 220 C. and 230 C. with an acid selected from the group consisting of maleic acid, fumaric acid, succinic acid, sebacic acid, adipic acid, phthalic acid, terephthalic acid, isophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and the anhydrides of said acids, said acid being, present in an amount that is substantially equivalent stoichiometrically to the amount of said partially esterified pentaerythritol reaction product, thereby forming an alkyd resin.

9. In the process of producing alkyd resins, the steps comprising heating and partially esterifying pentaerythritol with 1 to 2 moles per mole of pentaerythritol of fatty acids of oil having drying properties at a temperature between approximately 150 C. and 230 C. to form 1 mole of water of esterification per mole of acid, heating and dehydrating the partially esterified pentaerythritol at a temperature between approximately C. and 230i C. in the presence of an acid dehydration catalyst to forr'nvfrom 0.4 to 0.8 mole of water of dehydrationper mole of pentaerythritol thereby forming a, partially esterified, dipentaerythritohcontaining pentaerythritol reaction product, and thereafter heatingsaid partially esterified reaction product at a temperature between approximately 220 C. and 230 C. with phthalic anhydride, said phtha-lic anhydride being present in an amount that is substantially equivalent stoichiometrically to the amount of said partially esterified pentaerythritol reaction product that is present, thereby forming an alkyd resin.

10. In the process of producing alkyd resins the steps comprising heating and. partially esterifying pentaerythritol with about 1.3 moles per mole of pentaerythritol of soybean oil fatty acids at a temperature between approximately 150 C. and 230 C. to form I mole of water of esterification per mole of pentaerythritol, heating and dehydrating the partially esterified pentaerythritol at a temperature between approximately 150 C. and 230 C. in the presence. of a catalytic amount of ptoluenesulfonic acid to form from 0.4 to 0.8 mole of water of dehydration per mole of pentaerythritol thereby forming a partially esterified dipentaerythri'tol-containing pentaerythritol reaction product, and thereafter heating said partially esterified reaction product at a temperature between approximately 220 C. and 230 C. with phthalic anhydride being present in an amount that is substantially equivalent stoichiometrically to the amount of said partially esterified reactionproduct that is present, thereby forming an alkyd resin.

' References Cited in the file of this patent 

1. THE METHOD OF PRODUCING PENTAERYTHRITOL REACTION PRODUCTS WHICH COMPRISES THE STEPS OF HEATING AND ESTERIFYING PENTAERYTHRITOL WITH 1 TO 2 MOLES PER MOLE OF PENTAERYTHRITOL OF A MONOCARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF FATTY ACIDS CONTAINING 6 TO 18 CARBON ATOMS, BENOZIC ACID, AND MIXTURES THEREOF AT A TEMPERATURE BETWEEN APPROXIMATELY 150*C. AND 230*C. TO REMOVE 1 MOLE OF WATER OF ESTERIFICATION PER MOLE OF ACID AND HEATING AND DEHYDRATING THE PARTIALLY ESTERIFIED PENTAERYTHRITOL AT A TEMPERATUTE BETWEEN APPROXIMATELY 150*C. AND 230*C. IN THE PRESENCE OF AN ACID DEHYDRATION CATALYST TO REMOVE FROM 0.4 TO 0.8 MOLE OF WATER OF DEHYDRATION PER MOLE OF PENTAERYTHRITOL THEREBY FORMING A PARTIALLY ESTERIFIED DIPENTAERYTHRITOL-CONTAINING PENTAERYTHRITOL REACTION PRODUCT. 